Re: Parallel Port

["Ed Falis" <falis@gnat.com>]

"Philippe Bourzeix" <philippe.bourzeix@free.fr> wrote in message
news:172B4.2690$wl2.12638330@nnrp4.proxad.net...
> I have already asked some questions, but i would like to know why this
> program works on Alsys and not on objectada :
<snip>
>     function Entier_Octet is new Unchecked_Conversion
(Entier_8_bits,Octet);

<snip>

>     Registre_1, Registre_2, Registre_3 : Octet ;
>     for Registre_1 use at Integer_Address(16#378#); -- Parallel port
address
>     for Registre_2 use at Integer_Address(16#379#);
>     for Registre_3 use at Integer_Address(16#37A#);

<snip>

>     procedure Ecrire (Caractere : in Character) is
>     begin
>         Registre_1:=Dico(Caractere);
>         Registre_2:=Entier_Octet(2#0000_0000#);
>         Registre_3:=Entier_Octet(2#0000_0000#);
>     end Ecrire;

I don't see how this could have worked for either compiler, assuming x86
architecture without memory-mapped I/O (which can be inferred from the
standard PC I/O space address used for the port base).

You need to use port I/O instructions to read and write these addresses.
Take a look at Machine_Instructions_386.  If you're running on NT or Win2K,
it won't work in either case, because of OS hardware protection.

- Ed